Pond Collection

All vertebrates have internal skeletons, composed of cartilage only or bone and cartilage; both tissues contain living cells supplied by nerves and blood vessels. Bone is composite of protein, mostly collagen, and mineral crystals, mostly calcium phosphate Ca10(PO4)6(OH)2. Bone can grow, repair and remodel itself under the control of hormones. The density, rigidity and other mechanical properties are very diverse, reflecting the proportions of organic and inorganic material and their arrangement around blood vessels. Often, as in these sections of a small cattle leg bone, an outer layer of dense bone surrounds inner cancellous bone with more blood vessels and other soft tissue. In terrestrial vertebrates (and a few fish), the larger bones contain red marrow which produces erythrocytes and some leucocytes, and white marrow, adipose tissue containing storage triacylglycerols. These fats, and those stored in white adipose tissue elsewhere in the body, plus calcium and other minerals can be which is reclaimed from the bones into the blood stream during starvation, lactation or other metabolic stress. 

Teeth, here of a Nile crocodile, are similar in chemical composition to bone but harder and stiffer, with different cellular structure and mode of growth. The crown forms as two or more layers; dentine is secreted from long processes of cells with cell bodes in the roots and central pulp cavity which contains also nerves and blood vessels, and harder enamel and the cementum are deposited from cells on the outside of the tooth. Once formed, the minerals in teeth cannot be reclaimed, though the roots may close, cutting off blood and nerve supplies so the tooth falls out. The means of replacement of worn or damaged teeth is an important difference between the major groups. In most terrestrial vertebrates, the jaws and nose are integrated into the skull which supports the powerful biting muscles, as in this Nile crocodile. 

Long bones are linked by synovial joints which enable extensive movement, as in this humerus from front flipper of an adult sea turtle. The bone lengthens at growth plates (epiphyses) under the joints enabling the limb to function as it matures. Broader, flatter bones are joined by sutures that are initially almost straight, enabling growth at the edges, but they are mechanically weak. The sutures gradually become more convoluted and thus much stronger: the elaborately frilled sutures between the thick bones of this sheep’s cranium (braincase) indicate that he was a mature ram with substantial horns, deployed in contests with rival males.  

The internal skeleton comprises the skull & jaws, vertebrae with ribs in the thoracic region; those shown are from a parrotfish and a badger, plus bony fins in fish and the girdles and limbs of tetrapods. The pentadactyl (5-digit) limb, exemplified by a young iguana, is the basic form for all tetrapods (amphibians, reptiles, birds and mammals) and has evolved to perform many different functions.  

The vertebrate skin is collagenous, often including ‘dermal’ bone, and many nerves and blood vessels which in reptiles, birds and mammals, is covered with keratin, a tough, dry, low-density protein, usually incorporating pigment cells called melanocytes. This layer grows continuously as it wears or is shed and forms scales, hair, feathers and the outer horny components of beaks and claws. In this dorsal fin of a pilot whale, the black hairless skin overlies fibrous adipose tissue, supplied from two central arteries, plus smaller blood vessels and nerves.  

The chelonian (turtle) shell consists of the thoracic vertebrae fused to each other, to the ribs and to the overlying dermal bone. The different origins of the two layers of bone are clearly visible in these carapaces (upper shell) of a snapping turtle (upside down) and a softshell turtle, both freshwater predators. The keratinous layer of scales forms a pattern that is not congruent with the sutures between the bony components, as seen in the complete shell of a semi-aquatic turtle.  

As well as support, protection and leverage, stiff bone is also essential to hearing in almost all terrestrial vertebrates (and their aquatic descendants) e.g. the ear bones of a manatee, a large herbivorous mammal living in shallow seas and estuaries in the Caribbean. 

All mammals generate enough heat internally to be warm-bodied, at least for part of their lives. The keratinous outer layer of skin forms hair, incorporating black, brown or yellow melanin, as in this sample from a roe deer, consisting of outer protective guard hairs and dense, fine insulating underfur, kept water repellant by oily secretions from the sebaceous glands adjoining the hair follicles. Other functions of hair and how mammals keep their coats in good condition plus some human uses of animal skins are explained with many more specimens in the two lower Shelves of Oak. Prickles, bristles and spines, such as this American porcupine, are thickened hairs, as are whiskers which have sensitive nerves attached to their roots. The outer layer of claws (see lion & cheetah, Box B2), nails, horn and hooves are also keratin and thus withstand wear and injury by continuous growth. 

Mammals are endothermic, producing enough heat internally to maintain the body temperature significantly above that of their surroundings; normal body temperatures of humans and most other advanced mammals is about 38 oC, but can be lower and more variable in more primitive groups.  In contrast to amphibians, reptiles and nearly all fish are ectothermic, absorbing most of their body heat from sunshine and their surroundings. All metabolic processes, strenuous movement, digestion, growth etc. produce additional heat in all animals.  

Brown adipose tissue, a thermogenic tissue unique to mammals, oxidises glucose and fats in a way that generates heat (i.e. it consumes fats while white adipose tissue takes up and stores fats) and is under neural control so it is activated only when required. It can supplement other sources of heat, thus contributing to maintenance of normal body temperature, especially important for the brain, heart, kidneys and other vital organs. Most mammals, especially small mammals, have brown adipose tissue throughout life; it helps to keep them warm during sleep and is essential to rewarming at emergence from hibernation and torpor, when the metabolic rate, as measured by oxygen uptake, can be as high as in prolonged fast running. The tissue is mostly around the neck and shoulders of humans, hence the efficacy of shawls, scarves and shawls for keeping peoples’ whole body warm, but it often atrophies with age, especially in those who live mostly in heated buildings and enclosed vehicles. 

Another unique feature of mammals is the external ear (pinna), also seen in the roe deer specimen; pinnae are moved by muscles attached to the cranium to focus sound onto the middle ears with 3 ear bones, see Box A4, and in many species also serve in social communication, indicating emotions such as anger and fear. The necks of almost all mammals (including giraffes!) are supported by seven cervical vertebrae; the first five from the roe deer are shown, including the atlas vertebra that articulates with the occiput at the back of the skull.  

Mammalian backs flex vertically, as shown by the lower spine and pelvic girdle of an adult lion, in contrast to those of all fish, crocodilians, lizards & snakes, which flex horizontally from side to side (see Boxes D2 & D4). The lumbar vertebrae with their long stout transverse processes support strong muscles, essential for galloping and leaping. The sacrum, formed of fused vertebrae, articulates with the last lumbar vertebra, laterally with pelvic girdle at the sacroiliac joints and with the first caudal vertebra that are smaller and allow a much wider range of movements e.g. ‘tail wagging’. Mammalian groups have different numbers of thoracic, lumbar and, especially, caudal vertebrae, from 3-5 fused to form the coccyx in ourselves, to over 50 in pangolins and large whales. 

Many mammals, including the lion, retain the basic pentadactyl (5 toes or fingers) foot (see Box A1), but in other groups, one or a few digits dominate. This lower right foreleg of a horse consists of a single digit, corresponding to our middle finger, with the vestigial 2nd and 4th digits fused to its proximal end. Tendons around the phalanges (finger bones) form shock absorbers, and the bony core of the hoof is covered with hard, wear-resistant keratin equivalent to a claw or fingernail.  

Mammalian teeth form in sockets in the jaw bones, suspended by stout ligaments and are arranged in functionally matching groups in opposing jaws, as in the tiger. They are diverse in form and function, and in the timing of their growth and eruption. Biting incisors at the front, stabbing canines at the side and molars behind often folded to form ridges of different hardness to form ridges, enabling them to chew tough vegetation. In this juvenile camel, a bisected incisor tooth with its large pulp cavity is partially erupted, and its ridged premolars are emerging from their sockets, with the back tooth still forming inside the jawbone. The nasal cavity above the jaw contains many bony turbinals over which air passes on its way to and from the lungs. These structures are important for water conservation and for the sense of smell (olfaction).  

The two major groups of mammals, eutherians and metatherians, are viviparous (give birth to live young) as are some snakes, lizards and certain fish including many sharks. But lactation, feeding neonates on milk secreted from mammary glands, is the universal feature of mammals, including the monotremes (platypus and echidna,) which lay eggs like reptiles). The liquid diet enables the emergence of the first ‘milk’ set of smaller teeth to be postponed until the infants’ jaws have grown large enough to accommodate them. Compare the skull & jaws of the neonatal and adult lions in Box B2: the cub’s unerupted teeth forming in their sockets can be seen in its jaws, which are small relative to the large brain and eyes. 

In most mammals, as the jaws and skull grow, the milk teeth are followed by those of the adult dentition which lasts for the rest of their life: broken, worn or decayed teeth cannot be replaced (in contrast to fish and reptiles, see Box D4). This tiger was less than 2 y old, its skeleton was still growing, and it relied upon food provided by its mother. In the left lower jaw (see red mark), the first premolar of the milk set is being shed, its roots and their attachments to the bone have atrophied, so the erupting permanent premolar underneath easily displaces it. The sutures between its skull bones are straight, allowing for further growth; those of the premaxillae that hold the incisor teeth at the front of the upper jaw were so immature that the joints have fallen apart on drying. The canine teeth have erupted, but their pulp cavities were still large because the strong inner layers of dentine were not yet fully formed, so they have split as they dried. One has fallen out, revealing its internal structure: although the dentine is thicker near the tip, the tooth was probably strong enough to kill only small prey.  

Milk is produced only by the mother, synthesized in mammary glands in the skin from nutrients obtained via the blood from her diet and/or from her body reserves. Proteins come from depleting muscles and other tissues but fats are stored in white adipose tissue, distributed between several different superficial depots, in the abdomen, around the heart and in bone marrow. Lactation requires much metabolic effort and can be a major drain on the mother's reserves of energy and minerals, especially calcium which is reclaimed from the bones into the blood stream then into the milk, sometimes causing significant weakening of the bones. Milk synthesis, like all metabolic processes, generates additional body heat. After weaning, the mother may continue to protect her young, often bringing food or helping them find it. The young grow very fast while suckling, more slowly after weaning and usually very little after sexual maturity. 

Because the neonates do not need special foods in the way that most bird and reptile hatchlings do, lactation plus other forms of parental feeding enable mammals to breed on any diet, and thus in any habitat, that can sustain the adults, greatly extending their range and capacity to colonise new areas. Prolonged parental care also facilitates the evolution of large brains and complex sense organs, as seen in the camel.  

Suckling neonates have strong lips and facial muscles that are retained into adult life, so most mammals have soft, flexible faces that contrast with the hard immobile features of reptiles and birds. The lips and cheeks change the shape of the mouth, creating facial expressions, and modulate growls, whines, whistles, yelps and in humans, speech. These sounds combine with postures and movements, especially of the tail and ear pinnae, and facial expressions to convey messages within and between species that establish hierarchies, maintain contact within social groups and signal danger. 

Mammalian babies born in nests often have little or no hair, and even when fully furred at birth, like calves, fawns or foals, their small size makes them susceptible to cold. Nearly all are born with much brown adipose tissue that is activated within minutes of birth and, especially if they cannot absorb warmth from contact with the mother, a large proportion of their energy expenditure supports thermogenesis. As the infants’ muscles grow, shivering becomes an important way of producing heat, and insulation improves as the fur thickens. 

The avian skeleton is very light and strong, with hollow long bones strengthened with internal struts. More than 100 Mya, bird ancestors abandoned heavy teeth for lighter beaks consisting of horny keratin overlying the jaw bones. Bird beaks are very diverse in form, reflecting their diet which varies from tawny owls hunting mammalian prey to toucans gathering fruit and insects. They also incorporate sense organs, from which nerves pass through the tiny holes on the edge and tip of the jaw bones, as seen in beaks of the mute swan and flamingo, which find food mainly by touch and olfaction when dabbling underwater. This king penguin’s long pointed beak caught fish in the rough Antarctic Ocean, often in the darkness of the polar winter guided by such sense organs on the beak, see tiny nerve holes in the jawbones. Also visible are holes for blood vessels that supply the supraorbital salt glands in the grooves behind and above the eye sockets. These kidney-like structures, also present in other marine birds including albatrosses, petrels, pelicans, puffins and terns, concentrate the excess saltwater ingested with the food, excreting the salt crystals through the nose. 

Passerines and many other birds have three forward-pointing toes opposed by a fourth toe. Owls and many other raptorial birds have strong flexible feet tipped with sharp, curved talons enabling them to seize prey, carry it in flight, and hold it while tearing it with the beak (see Box D2). Parrots’ feet grip food and perches with two central toes opposite two outer toes. 

The spinal column has many contrasts to that of mammals. As shown by the cervical (neck) vertebrae of this flamingo (tied in anatomic order), any number of vertebrae can form long, flexible necks; most birds can twist the head round to look behind them. Bird backs are rigid and relatively short. Several fused vertebrae with ribs extend to the much-enlarged breastbone that forms the keel to which large flight muscles are attached. The stout pectoral girdle includes the ‘wishbone’ and components that articulate with the keel bone. The powerful flight muscles (‘white meat’ in poultry) run from the keel bone and pectoral girdle to the bones of the forelimbs that form the wings.  The lumbar vertebrae and sacrum are fused to the large pelvis which supports the muscles that move the legs and tail. Observe these bones disarticulated from this mute swan, one of the heaviest of all flying birds, and in situ on the mounted skeleton of an African grey parrot. This specimen lived with the compiler of this collection, acquiring a vocabulary of over 100 words, until she died aged at least 44 y.  

All birds are endothermic and lay eggs that are incubated by their parents’ warm bellies, usually by both adults taking turns. Many species build nests, such as that of this blackbird, but others rear their offspring in cups built of saliva, in holes in trees and banks, and on cliffs and bare ground. Marooned within its egg, bird embryos utilize the nutrients in the yolk and absorb minerals from the inside of the shell, thus both building their skeletons and facilitating hatching. Ostrich chicks are strong enough to run and feed themselves within minutes hatching; thin-shelled eggs nurtured such chicks but the thick rings were made from infertile eggs in which no embryo developed. 

Nearly all birds provide protection and warmth to their hatchlings and most bring them water and food, which in many species is quite different from the adults’ diet; for example, many birds that eat fruit, seeds or other plant parts as adults feed their young on protein-rich insects, calcium-rich snails or other highly nutritious, seasonally available foods. Many birds migrate long distances to breed where they can find large quantities of ‘baby foods’ on which to nourish their offspring. The close contact between parents and nestlings in compact nests enables ectoparasites, of which several groups infest birds, to pass between generations. The nestlings grow fast while their parents are feeding them and the skeleton is often almost full size, with sutures fully closed, at fledging or soon after. But sexual maturity may be delayed, especially in large species, while the young, who often have distinctive juvenile plumage, acquire the skills necessary for successful breeding. Some raptor parents may actively teach their offspring how to hunt. 

Pigeons of both sexes feed their young chicks on a deciduous tissue from the throat as well as on partially digested food. It’s called ‘pigeon milk’ but it is not a secretion like mammalian milk (though the endocrine controls are remarkably similar). However, as in mammals, this capacity partially emancipates parents from collecting special foods for their young, thus enabling such birds to breed well in artificial habitats such as cities. 

Feathers are keratin that, like mammalian hair, grow into various forms from groups of specialised cells in the skin. The plumage requires frequent maintenance, ‘preening’, in which oily secretions from the preen gland under the tail are spread over the feathers with the beak, for cleaning, waterproofing and to repel ectoparasites. 

Large feathers with a straight, stiff rachis from which barbs extend are the main agents of flight. Their roots, which contain nerves and blood vessels, are moved by muscles attached to the bones, as seen in the pigeon wings and tail, and in the parrot, enabling rapid adjustments to the shape of wings and tail essential to powerful, agile flight.  

Body feathers are similar to small wing feathers, often brightly coloured and of diverse form, especially on the head, and underlied with down. This flightless emu has short and floppy outer feathers that resemble down (see also Box C1), which are small fluffy, usually unpigmented, feathers without long rachis that form excellent thermal insulation under the stiffer body feathers. Muscles on the rachises of outer feathers contract during cold nights to ‘fluff up’ the plumage, and also to appear larger in combat, or to expel excess water (or air). Evidence from fossils and embryology shows that feathers first evolved in small Triassic dinosaurs as down that kept hatchlings warm. Gradually larger body feathers became indicators of sexual and social status in adults, before flight feathers evolved in the first true bird 100 Mya later.  

Insulation is important because birds generate enough heat internally to be warm-bodied, usually to a slightly higher temperature than mammals. Bird legs consist of skin, bone and tendons, tissues that can tolerate cold, and are moved by muscles in the warm body. Parallel blood vessels that act as heat exchangers control warmth from flowing out of the body into their featherless legs, which thus remain cool. Admission of a little warm blood protects the legs and feet from freezing when standing on ice; increased blood perfusion dissipates excess heat when required, supplemented by panting. Birds can shiver but do not have brown adipose tissue. Many small nestlings cool while their parents are absent, which saves metabolic energy but slows growth. In a few species, adults also cool when bad weather prevents foraging, briefly becoming torpid. 

Flight and body feathers usually incorporate pigments and may be moulted, sometimes several times a year, often with different pigmentation in the replacement plumage. Black, grey, brown and yellow are usually melanin (as in reptiles and mammals) but other pigments that may be derived from the diet, as in scarlet tanagers, which eat fruits rich in carotenoids, or from algae and brine shrimp that pink flamingos sift from salt lakes. In some groups, including the parrot family, feather pigments are synthesized from special genes, and thus retain their brilliant blue, green and red plumage even in captivity. The wing and body feathers of African grey parrots are black to grey and the tail is scarlet, but after the age of about 30 y, the red pigment replaces melanin in other feathers, producing a mottled appearance. This phenomenon, probably comparable to hair turning grey then white in elderly people and dogs, was noted by aviculturalists more than 200 y ago, but its causes and function are not known. Shimmering colours, as in peacock tail feather, are ‘structural’, created by intricate microstructure of the keratin. 

The limited evidence suggests that the evolution of sound production, culminating in bird song, evolved in parallel, with both plumage and calls becoming essential to inter- and intraspecific communication and indicators of age and, in adults, sex and breeding condition. Birds make a wide range of sounds that claim and hold territory and nest sites, attract mates, alert other flock members to danger, and for parent-offspring interactions. Many species learn to recognise their parents’ calls before they hatch out of the egg. 

Birds have excellent sight, including seeing colours, and hearing, especially tawny owls with large eyes that point forwards for highly sensitive binocular vision and capacity to locate sound sources. The feathers, on the legs as well as the wings and body, are soft and down-like, enabling owls to fly silently. Found almost worldwide, owls are highly specialized, mostly nocturnal predators that locate prey by sound and by sight, pouncing onto it quietly.  

Penguins cannot fly but are agile swimmers, flapping their stout wings covered in tiny, smooth feathers and steering with their large feet, and can dive to greater depth than other seabirds. Their strong legs and feet tipped with stout claws enable them to climb up icy cliffs and onto icefloes. Excellent feather insulation and mechanisms that control heat flow to beaks, feet and wings enable the congeneric Emperor penguins to breed in some of the coldest environments on Earth.  

Horny beaks, scales on legs and claws on feet grow, replacing wear and damage, enabling birds to live much longer than similar-sized mammals. Since the 1890s, many birds have been individually marked as nestlings with numbered leg rings recorded on central databases. So more is known about the longevity in the wild (as well as in captivity) of more species of birds than of any other group.

The two major groups of fish, Chondrichthyes, sharks, skates and rays with skeletons of cartilage, and bony Osteichthyes swim, feed and breed in many different ways.  

The cartilaginous jaws of this juvenile great white shark show how the biting teeth form and are continuously replaced throughout life, becoming larger as the fish grows into an apex predator. Large sharks can produce, and shed, as many as 500 teeth in a lifetime, so sharks’ teeth are common as fossils. Fish teeth are not confined to the mouth, as in this sawfish rostrum, which is deployed to slash at prey and dig in sand to find food, and many fish have teeth on the gill arches in the pharynx (throat). Large fish and reptiles such as crocodiles and alligators bite prey with sharp pointed teeth, then break it up with twisting or tearing movements of the body and limbs. 

Most extant primitive bony fish, such as this this gar fish, also catch small prey in their many sharp teeth of various sizes. The body scales consist of a core of dermal bone (see Box A4) covered with a thin layer of a smooth, hard material resembling too enamel. The far more abundant and diverse teleost fish have a huge range of body forms and bony scales, as shown by the porcupine fish, parrotfish and large marbled cichlid, reflecting varied diets, swimming styles and habitats. Much of the body is swimming muscles attached to the central vertebrae, girdles and ribs.  

The long processes extending from this vertebra of a fast-swimming, predatory tuna support powerful muscles, some containing the oxygen-binding pigment myoglobin, hence their dark red colour. It catches other fish in open water but some teleosts, including this catfish, have flattened bodies and forages in or near the bottom. Boxfish rely upon a rigid body, formed of dermal bone (see Box A4) to protect them as the swim slowly sucking up small morsels. Some fish like this parrotfish nibble encrusting algae, sponges and coral, a few, including this sheepshead, grind molluscs and crustaceans with teeth that look remarkably like those of humans.  

The earliest terrestrial vertebrates were Devonian amphibians with adult body form similar to this mudpuppy salamander with a long flexible body & tail and short limbs. Anurans (‘tail-less’), such as this African clawed frog, now the most abundant and diverse group of amphibians, first appeared in the Triassic 150 My later. All extant species have thin, permeable skin and live on land and/or in freshwater. The adults swim and walk on strong legs, are mostly predators and communicate by airborne sounds. The territorial and courtship calls of some males are remarkably loud, amplified by expandable vocal sacs. In most newts & salamanders and frogs & toads, externally fertilized eggs are deposited in ponds, hatch into tadpole larvae that eventually metamorphose into the adult form. But anuran parents have various ingenious ways of protecting their offspring from predation and desiccation, including sticking the spawn to leaves or embedding it in their skin, or laying single eggs in tiny pools inside flowers or tree holes. Many large species, especially the females, may take a decade to reach sexual maturity after metamorphosis, but they can have long lives, more than 20 y under good conditions for this clawed frog. 

The cleidoic egg that is laid on land is a unifying character of reptiles that have diverse body forms. This egg was laid into a hole that its mother, a large tortoise, dug in a sunny place; its shell is waterproof but permeable to oxygen and carbon dioxide. It encloses everything the embryo needs to develop, during incubation warmed by the sun that can last months, into a miniature adult, without any larval stage. Most extant reptiles breed on land, digging holes in which to deposit their eggs, though a few squamates (lizards & snakes) are viviparous, incubating the eggs inside the body then giving bird to live young, as were several extinct groups of Mesozoic marine reptiles, notably ichthyosaurs.  

Almost all reptiles that live in temperate climates stop eating for a few weeks to empty the gut, then hibernate, sometimes for many months, while it’s too cold to find and digest food, emerging in spring to warm themselves by basking in sunshine.  

The most ancient major group of extant reptiles are the chelonians, which emerged in the Triassic with toothless jaws which form a stout horny beak as seen in the sea turtle, which also shows the ear cavity behind the superficial eardrum, just behind the jaw articulation, as in ourselves. The girdles support short strong limbs inside shells, formed as shown in Box A1 and A4, and the outer layer of tough keratinous scales makes the skin impermeable to water. All breathe air in lungs expanded by muscles attached to the inside of the shell and movements of the legs, and in the mouth and throat. Aquatic chelonians mate in water but all females return to land to breed; those of oceanic species swim huge distances to deposit their eggs on the same beach on which they hatched perhaps 50 y earlier. The tiny hatchlings emerge at night and move at once towards the sea where they fend for themselves; note that this Pacific Ridley’s turtle hatchling already has its hard, ridged shell. As for all reptiles, the habitat must provide foods suitable for all growth stages to sustain a breeding population. In contrast to birds and mammals, most fish and reptiles start breeding before they have grown to their maximum size. 

Terrestrial chelonians are almost all herbivores, grazing on flowers and leaves, those living in freshwater rivers and pools and in the sea eat a mixed diet, including preying on fish and other animals. As in all reptiles, they have few facial muscles except jaw muscles and to open and close eyes, so the face is firm with limited capacity for facial expression compared to mammals. Most chelonians have long necks that allow the head to be extended, or retracted, often very fast, into the shell. Their body form may appear ungainly compared to lithe fish, snakes and mammals but for their size, chelonians are some of the longest-lived vertebrates known. Furthermore, the sparse records reveal that apparently closely related species have widely different lifespans, leading scientists to investigate the ecological and molecular bases of longevity.  

The teeth of lizards and snakes (and many extinct reptiles) grow from bone as in this omnivorous tegu lizard and their lithe bodies are covered with small scales. Teeth of crocodilians, such as this alligator, form in sockets as do those of mammals, but are replaced many times as they grow. Their scaly skin is reinforced with hard scutes, ridged on adults’ backs, formed of dermal bone (see Box A4); many extinct reptiles, including dinosaurs, were also thus ‘armoured’.  

Crocodilians live in and near lakes and rivers with a few species hunting in coastal seas when adult. Their diet progresses from insects and crustaceans as hatchlings, then to fish and birds of increasing sizes before they can tackle mammals, often by lurking just below the surface as prey come to drink or traverse rivers.  

Almost all lizards are terrestrial predators with excellent visual acuity and colour vision; they eat mostly insects and other arthropods, including the desert spiny lizard, but a few prey on insects when small but eat soft vegetation as large adults (see Box C4). During breeding seasons, males of some species develop colourful scales with which they display to each other and to females. 

The Galapagos marine iguana are the world’s only marine lizards; they dive into cold shallow water to graze algae encrusted on rocks before returning to the shore where they sunbathe to rewarm, and expel excess salt from nasal glands similar to those of seabirds (see Box C4). 

Snakes are limbless; their various styles of movement all depend upon muscles attached to the single row of wide scales in the ventral skin, seen in this little ground snake, and the underlying ribs and spine, and upon the strong body muscles, with which they can entwine themselves around branches etc. Oak 3rd Shelf shows more about reptile skins and scales.  

All snakes are predators which kill their prey (see Box D2) then swallow it whole. The jaw hinges and the joints between two halves of both upper and lower jaws can be dislocated, enabling each of the four jaws to be moved independently; ingestion can take an hour or more as the jaws are ‘walked’ over the prey, gradually pulling it into the throat. The expandable mouth means that when not swallowing, snake heads appear surprisingly small compared to the wider body. 

Most predatory vertebrates eat invertebrates and/or carrion when small. Insects, spiders and other terrestrial arthropods are abundant and supply plenty of protein, but almost no bone-forming minerals, which can be obtained from shelled molluscs or marine crustaceans. Earthworms, whose guts contain much earth as well as worm tissues, are a favourite food of small mammals, birds and fish.  

Preying on other vertebrates provides all necessary nutrients for obligate carnivores such as sharks, predatory teleosts, snakes, cats, raptorial birds such as owls & eagles, as long as the viscera and gut contents, plus some bone, bone marrow and brain are also consumed (by eating only the muscles of mammals, birds and fish, modern humans miss many important nutrients that these animals could supply). But there are snags: parasites are ingested and develop in the gut, as those found in the python (see Box D2), and some species burrow through the gut wall to invade other tissues. Selective butchery and cooking save humans from similar infestation. 

Animals have a very wide range of strategies for catching, dismembering and ingesting their each other. Predation risks injury to the predator as well as to the intended prey. Healed wounds are often found in the skeletons of wild vertebrates, see Oak 2nd Shelf. 

Stoats, weasels, mink, polecats, pine martens, otters, wolverines (see Oak bottom Shelf), badgers and many other small carnivores are mustelids, agile climbers and burrowers that prey on large insects, worms, snails and small vertebrates such as rabbits, hedgehogs, lemmings, voles other small rodents (see Box D3) and nesting birds. Badgers have a mixed diet, including grain, roots, earthworms and molluscs which wear the teeth, as in this old male. They live in family groups that communicate with whistles and other calls. Otters hunt fish and large invertebrates in rivers, lakes and rocky seashores, also often in family groups. 

 Most mustelids, even small species, remain active hunters throughout the year even in very cold climates. Stoats occur throughout northern Europe & Asia, Canada and coastal Greenland; in snowy regions, their brown summer coat is shed before winter, replaced, except for the black tip of the tail, with fine white camouflage fur called ‘ermine’. At c. 10 kg body size, badgers are too big to hibernate but during cold spells, they retreat to their underground dens where they become torpid like bears. 

Although clearly Carnivora, most bears have a mixed diet of plants, fungi and small prey; for example, brown bears are omnivores, eating fruit, nuts, grass and carrion as well as fish and mammals. Their natural range, now much reduced, was huge: almost the whole of Europe, Asia and western North America above about 40 oN, including most large islands except Ireland and southern Japan. Pandas feed almost entirely on bamboo shoots, supplemented with a little carrion and their small natural range is declining.  

Ursid feet, here from a North American black bear, have stout, non-retractable claws and are plantigrade, with the heel on the ground and large pads of fibrous fat. Coatis & raccoons (New World Carnivora) and humans are among the few mammals to have similar feet. The skeleton enables them to assume various postures, including standing upright with forelimbs hanging (thus resembling a hairy man), and they can climb trees, dig for roots and open bees’ nests – most bears really do like honey! Bears can run fast over almost any terrain but only for short distances, as their thick shaggy hair (see Oak lower Shelf) makes them susceptible to overheating. 

Polar bears are closely related to brown bears, but are specialised to life as predators and scavengers at the edge of the arctic sea-ice and on tundra. Their feet are disproportionately broad, with much more hair and the exposed skin has a non-slip surface, and the ears and tail are shorter. They are strong swimmers, as illustrated by this humerus to which powerful muscles are attached. Polar bears eat carrion and a little seaweed only when their main prey is unobtainable. Their excellent sense of smell and hearing enables them to find the breathing holes that seals make in the sea-ice, then they wait beside them, grabbing the prey with canine teeth that are longer and stronger than those of other bears. Only lactating mothers and cubs eat all of the seals they kill; large males eat the blubber and some of the gut contents, but little muscle, probably because energy is more easily generated from fats than from proteins. Although these bears’ food is very high in fat, and when plenty of food is available, they become obese, there is no evidence they suffer from cardiovascular and metabolic diseases associated with such diets in humans.  

Exceptionally for Carnivora, polar bears do not establish territories (food availability in the erratic arctic climate is too unpredictable); they roam huge distances and the mature males fight with rivals for mating rights. Consequently, extreme sexual dimorphism has evolved, with males growing up to three times the size of breeding females. The males are active all year round and may steal prey from smaller bears, including mothers, and kill any cubs they meet. An anatomical correlate of this social structure is displayed in Oak top shelf. 

To avoid encounters with predatory males, pregnant female polar bears fatten on seals during the autumn, then migrate inland, away from their food source. They dig a snow den, often on a hillside, where they give birth to twins or triplets in mid-winter. Ursid neonates are smaller, relative to adult size, than those of any other mammals. The mothers stay in the den, feeding their offspring on very rich creamy milk, without eating or drinking themselves, until the spring when the cubs are large enough to cope with the journey back to the coast. The cubs may continue suckling, plus eating prey killed by their mother, for several years until they are nearly fully grown, one of the longest periods of infant dependency, and are a major drain on the mother’s reserves of energy, and bone minerals. Although the dynamics of deposition and withdrawal of storage fats differ greatly between adult males and females, no sex differences in the distribution of their adipose tissue were found. 

Bears are too big to hibernate but those native to seasonal climates may fatten up for several weeks before entering caves or other secluded retreat, where they sleep for long periods, allowing their core body temperature to fall up to 7 oC from normal so their energy reserves are utilized slowly. Polar bears reduce their energy expenditure in similar ways during their summer fast when melting sea-ice makes seals impossible to catch.

Felids are obligate carnivores that are incapable of digesting more than a little plant material. The big cats are all specialised predators with long sharp canine teeth that stab prey and molars at the side of the jaw form scissors that slice the meat, though they also eat the viscera and gut contents of their mostly herbivorous prey from which they obtain essential nutrients. Small and medium sized cats like this South American jaguar usually hunt at night; a reflective layer at the back of the eye (‘cat’s eyes’) enables them to see well in the dark, their hearing and olfaction are excellent and they feel with numerous long, sensitive whiskers. The sensory nerves from the whisker roots pass through many tiny holes (seen in the jawbones of both this skull and the lion); the patterns they form are asymmetrical because nerves develop early in the embryo, then cartilage and eventually bone form around them. The nasal turbinals that support the olfactory mucosa and forward-pointing eyes are clearly visible in the lion skull and bisected cat skull illustrates the relatively large brain with the round auditory bulla below it.  

Most felids are solitary as adults except while breeding or briefly form small coalitions. But lions live in larger social groups, usually led by several related females that sometimes feed each other’s offspring, which are fathered by a dominant mature male. Hunting as a pack enables them to kill prey much bigger than themselves; a few prides even specialize on taking sub-adult elephants. The minimal wear to his fully erupted teeth suggests that this male African lion was a young adult, perhaps recently expelled from his natal pride. 

Felid claws, including those of lions, stay sharp because they are retracted into skin pouches while walking silently on soft flexible foot pads, or extended when required to grip prey or in climbing. Many medium-sized and small felids are bold, agile tree climbers, and sure-footed in mountains: leopards in Africa and Asia, puma, Canadian lynx & bobcat, jaguar and its smaller relatives, the ocelot & margay in the Americas, and two species of lynx in Europe and NW Asia. Cheetahs are exceptional felids with hard footpads and thicker, blunter claws like those of canids. They hunt more by speed than stealth; their feet are huge relative to their light, slender body with very long heel bones that enable fast galloping and stability in tight turns (compare with the lion limbs in Box B4). Some felid skins that are adapted to various habitats and hunting styles are displayed in Oak. 

With firm paws and non-retractable claws, canids can run further and, over long distances, faster than felids but are inadept climbers. Their digestive and metabolic capacities are much broader than those of cats. So although most hunt live prey, many species including the red fox also scavenge and eat some fruit, grain and other plant matter. Red foxes now one of the most widespread and abundant of all wild carnivores; they have adapted to urban habitats, breeding in parks, churchyards and other small spaces, raiding bins for scraps ‒ and helping to control rodent populations. The species was introduced to Australia in the mid C19th and has prospered, in spite of the hot dry climate, depleting populations of many native species. The smaller arctic fox that hunts and scavenges in cold mountains and arctic regions; it moults its fine, dense hair (see Oak) twice a year, being shaggy grey or brown in summer, and pure white in winter, extending to the soles of the feet. With the warming climate, the red fox’s range is expanding. outcompeting the indigenous arctic fox which is now abundant only on arctic islands. Many other canids are also in decline.  

The timber wolf hunts as a pack of a dozen or more adults to kill prey much larger than themselves. The species is very social, communicating with each other by a range of growls, whines and howls plus facial expressions and postures of the body, ear pinnae and tail. Its range was previously similar to that of brown bears (see Box A2), but has been even more severely reduced during the past millennium. The smaller Ethiopian wolf is anatomically similar but less social, usually hunting alone for small mammals and birds. Its range is restricted to the Rift Valley and mountains of East Africa. 

Felids, and all but one canid species, are active throughout the year and cannot hibernate; they are not migratory, though some move long distances within a huge home range.

Cetaceans (and Sirenians) are the most marine of all mammals (a few small species of dolphin live in large rivers); they cannot support their weight in air and die from suffocation or overheating if stranded. Their pelvic girdles and hind limbs are vestigial, but the forelimbs form powerful flippers supported by large shoulder blades, and strong swimming muscles attached to the transverse processes of the vertebrae that move the long tail up and down (see the Minke whale in in the Foyer). The tail consists of many stout caudal vertebrae at the centre with wide flukes composed of fibrous adipose tissue covered in smooth, thick hairless skin, as in the long-finned pilot whale (a member of the dolphin family). The streamlined body with additional fibrous fins (see Box A4) enable fast, agile energetically efficient swimming. 

However, cetacean flippers and spine are too specialized to enable grooming, so they accumulate external parasites on the skin. Like other soft tissues, the exact shape of fins and flukes differs between individuals, and they acquire nicks and scratches, which serve as natural markers that identify each animal. The exertion of fast swimming generates much heat. Two large arteries visible near the skin of the pilot whale fin (see Box A4) may serve to dissipate excess heat, as do the short stubby limbs of pinnipeds. 

Cetacean skeletons, especially the skull and jaws, are much altered from the typical mammalian form. The nostrils are near the top of the head, as in these bottlenosed & white-sided dolphins, enabling them to snatch breaths at the surface while swimming very fast. Toothed whales, including dolphins, porpoises and long-finned pilot whale, have numerous similar peg-like teeth widely spaced on long slim jaws with which they catch fish, sea birds and sometimes other marine mammals. The relatively large cranium and foramen magnum at the back, clearly seen in the white-sided dolphin skull, contain the big brain and spinal cord. Its 7 cervical and 2 thoracic vertebrae are in anatomic order: the atlas vertebra is large and fits very closely to the back of the skull but the other cervical vertebrae are very narrow. The neck is short and the relatively large head could move only a little on the shoulders. Compare these vertebrae to those in Boxes B4 and C4.  

The orcas, or killer whales (members of the dolphin family), are found in oceans worldwide and hunt in pods usually led by an older female; some specialise on hunting seals, others on shoaling fish and some hunt juveniles of other cetaceans. Narwhals and the related belugas hunt fish, usually as a pod, in Arctic coastal waters and the edge of the pack ice. The left upper canine of this adult male narwhal forms a hollow spiral tusk that protrudes from the mouth which has only a few other small teeth. Its exact functions remain unclear.  

Cetaceans are intelligent with very sophisticated hearing, but olfaction, so important to terrestrial mammals, is vestigial and vision less important. Most odontocetes are social, living in pods that communicate with sounds generated by tail slaps and by grunts, whistles, clicks and screams; they also hunt prey by echolocation, emitting ultrasonic clicks and interpreting the echo, all dependent upon unique, complex mechanisms in the head and neck.  

Sound is generated by vibrating air expelled under tight control from the lungs (as in their terrestrial ancestors) but pairs of phonic lips replace the larynx. The sound then passes through the melon, a large pad of specialised adipose tissue situated on the dip in the skull in front of the nasal canals and over the upper jaws. Its internal structure is highly organised into channels of adipose tissue containing triacylglycerols with specific combinations of fatty acids that have slightly different densities and other mechanical properties. The melon focuses the sound into beams which can be directed like a torch towards items of interest. 

In toothed whales, sounds are received by adipose tissue inside the lower jaws (the fat-containing cavity is visible in the pilot whale jaw), which conduct them to the ears enclosed in capsules of bone beside the jaw hinges (seen in both dolphin skulls). External ears, or even earholes, are absent in all whales. 

In all the ‘great’ whales except sperm whales, the teeth are replaced with baleen, a keratinous tissue derived from hair, with which relatively tiny prey, krill, other invertebrates and small fish, are strained from the water. The skull is even more altered, with a huge mouth, half the length of the body in some species, with an enormous tongue that scoops up prey trapped in the baleen. Baleen whales feed near the surface or dive to depths of several hundred metres. Sperm whales and a few other toothed whales that prey on deep-sea fish and squid can dive to 2,000 m and stay submerged for over an hour. The faeces that such whales release near the surface bring nutrients up from the depths, fertilizing the phytoplankton. Conversely, huge whale bodies sink after death, supporting ecosystems on and near the sea floor.  

The great whales produce loud sounds with which they communicate over very long distances, and again specialized adipose tissue has important roles. Sound is produced by air from the lungs vibrating in the much-enlarged larynx, which is attached to a U-shaped pad of fatty tissue that redirects the air back to the lungs. Such ‘air recycling’ enables these whales to ‘sing’ for hours without surfacing to breathe.  

Whales evolved from terrestrial ancestors whose ears work well in air but not underwater. The ear bulla of baleen whales such as this fin whale is one of the densest, stiffest bone known: by complex, incompletely understood mechanisms, the bullae and the adjoining ears enable the whales to locate a wide range of underwater sounds. The other bone sample is cut from a fin whale vertebra, low-density bone permeated with adipose tissue containing storage lipids and other soft tissues.  

Pinnipeds are also predators, with sharp pointed teeth, widely spaced to drain seawater, and extensive nasal turbinals as in these skulls of grey seal and Antarctic fur seal. Most hunt fish in coastal waters, often entering estuaries; they dive to depths of hundreds of metres, staying submerged for tens of minutes but not for hours, and may haul out onto beaches to rest. Walrus tusks are upper canines, present in both sexes though bigger in males, that grow continuously throughout life. One of the largest of all pinnipeds, they dive to the bed of shallow arctic seas where they use their tusks to prise mussels and other large invertebrates from rocks. Local people have adapted this small walrus tusk as a tool, note the iron insert and strike marks, and decorated it with an Inuit scene. 

Pinnipeds are powerful, agile swimmers, combining up and down movements of the body with side-to-side movements of the hind flippers, that are held around the small tail. The forelimbs tipped with blunt claws are also important for locomotion, in some species for holding food while eating and, equally important, are deployed in scratching the whole body, thus removing loose skin and most external parasites. On land or in very shallow water, pinnipeds can walk on their short legs and relatively large hands and feet, or gallop using the body swimming muscles.  

Their large forward-pointing eyes can see underwater as well as in air and they sense vibrations of their prey with the many whiskers on the head that are attached to nerves which pass through the jaws and cranium. Since it functions in air as well as underwater, the ears are essentially similar to those of terrestrial mammals.  

They communicate with each other on land and underwater; flipper clapping and teeth chattering supplement barks, grunts and chirps produced by air passing the slightly modified larynx. Females assemble, sometimes in huge numbers, on beaches or icefloes to give birth, before mating again and returning to the sea. The much larger adult males may control a harem of breeding females, deterring rivals by roaring and/or fighting.  

Large pinnipeds have hairless skin, as do all cetaceans, but neonates and smaller seals such as the Antarctic fur seal have hair. The guard hairs are straight and smooth to maintain laminar flow of water, as in the little model probably made from the skin of a common (= harbour) seal.  

All seals have a layer of adipose tissue (blubber) under the skin that serves as an energy store, as in other mammals, and for thermal insulation. The fats themselves are no better as insulators than any other tissue, but cells in adipose tissue and skin metabolize slowly, so can be cooled and deprived of blood for a long time without harm. Loss of internal body heat is restricted by controlling the blood supply to these superficial tissues. When walruses emerge from the ice-cold water their skin is pale grey, without blood flow and with the dark melanocytes retracted. To warm up in sunshine, they expand these pigment-containing cells, becoming dark grey. But when they get too hot, they turn bright pink as melanocytes retract and warm blood flows into the skin, dissipating the excess heat at the body surface – as we do when overheated.  

Cetaceans give birth at sea but pinnipeds do so out of water. Some whales, including the largest, migrate long distances between rich polar feeding areas and warmer waters where they give birth. In both groups, the single calf grows rapidly on its mother’s very rich milk. Most seals abandon their offspring at weaning but many young cetaceans stay near their mothers until nearly fully grown, learning the skills needed for hunting and for socializing. Recent research reveals that some whales, especially arctic species, have a very long lifespan. 

Many other groups of mammals are also predators, including moles, hedgehogs and shrews, now classified as Eulipotyphla. 

Hedgehogs are nocturnal predators on earthworms, large insects and other small invertebrates, and also take eggs and hatchlings of ground-nesting birds. They can run quite well and are surprisingly agile climbers, but when alarmed they stop to hide under their stout spines (modified hair) by rolling into a ball. This defence works against foxes, raptorial birds and even humans, but not motor vehicles. The short limbs cannot easily groom the thick heavy skin on the back, which may harbour large ectoparasites. Breeding begins in early spring with males courting females with grunts and snorts until she flattens her spines for mating. Several hoglets are born in summer, but as in birds, all offspring are raised to weaning only with the most abundant food supply. During cold winters, hedgehogs hibernate in shallow burrows, compost heaps or under piles of logs. 

European moles are widespread and often abundant in fields and gardens but rarely seen, because they spend their whole life in underground tunnels, often several metres long, that they dig, expelling the excess soil to form molehills. Although almost blind, their acute hearing and olfaction enable them to find earthworms, burrowing insects and other soil invertebrates as they fall into the tunnels. The long mouth has the full mammalian complement of 44 teeth, and the saliva contains a toxin that can paralyse prey, which in times of plenty may be cached for later consumption. The humerus (both shown) has huge flanges to which strong shoulder muscles are attached, the upper parts of powerful forelimbs and disproportionately large ‘hands’ ending in stout claws that enable this tiny animal to dig through soil for which we would use steel tools. 

Nine-banded Armadillos (Xenarthra) are widespread in tropical South and Central America, southern USA. They dig for ants, termites and other burrowing invertebrates with their short but powerful limbs and 3-toed claws, scooping them up with their extendible sticky tongues. Small peg-like teeth crush larger prey including millipedes, centipedes and small amphibians. In most mammalian litters, each foetus develops from its own zygote but this species is almost unique in always giving birth to identical quadruplets, created from single zygote. The natural function of this unusual habit is not clear but since armadillos breed well in captivity, scientists exploit it for research into epigenetic changes and the effects of genes and the environment on physiology and behaviour.  

Bats (Chiroptera) are the second most diverse mammalian group after rodents and the only mammals capable of powered flight. In contrast to bird wings (Box C4), bat wings are double sheets of skin, supported by elongated finger bones, hind limbs and tail. Microchiroptera such as this pipistrelle are insectivorous, catching huge numbers of flying insects mainly at night, sometimes scooping them up with their wings and tail. They locate prey by echolocation, producing loud, high-pitched sounds and interpreting the echo, picked up by their very sensitive hearing. In many species, other ‘bat squeaks’ attract mates, establish territories and help mothers and infants find each other in the dark caves where they breed. Temperate zone bats hibernate during winter when flying insects are scarce, often in caves or unheated human constructions such as barns, church towers or derelict buildings. 

Most avian predators like this heron locate the prey with their excellent vision and grab it in their beak, sometimes tossing it before swallowing it headfirst. Large raptors such as eagles pounce of their prey from the air and the carry it in flight with their large strong feet tipped with sharp stout claws, which also hold it while the powerful beak tears it.  

Many lizards and turtles are predators, usually of large insects and other invertebrates when small, including this alligator snapping turtles (body mass 2.6 kg). Its wide head can be thrust very quickly from under the shell to full extension of its long, flexible neck; some of the cervical vertebrae are shown. The stout jaws tipped with sharp spikes (the premaxilla of upper jaw is missing in this young specimen) are worked by thick muscles in grooves flanking the central braincase. Adults, which grow to 50 kg or more, have a powerful bite, ambushing other turtles, frogs, ducklings and small fish in swamps and slow-flowing rivers of southeastern USA. Compare this skull with that of the herbivorous tortoise in Box D3. 

Many small snakes (see Box D4) are non-venomous and eat worms, leeches, slugs, insect larvae etc. plus small vertebrates. The juveniles of larger species have a similar diet, progressing to larger prey as they grow. Most big snakes are specialist predators on mammals and birds that they usually hunt at night or in burrows, locating the prey by olfaction and with paired pit organs which ‘see’ the infrared radiation (heat) that their homeothermic prey emit.  

The constrictors, boas in the Americans and Old World pythons, crush their prey by coiling their long bodies around its thorax, before slowly swallowing it whole, as explained in Box D4. Parasites found in the gut or lungs of this large python include, L to R: tongue worm, phylum Pentastomid (= Linguatulida); roundworm, phylum Nematoda; tapeworm, phylum Platyhelminthes, Class Cestoda. 

In venomous snakes, some salivary glands are modified to secrete venom, mixtures of toxic peptides that differ greatly between species, and inject it through fangs, hollow sharp teeth. Vipers like this rattlesnake have a pair of long fangs at the front of the jaw that are raised or retracted by muscles and, like all reptile teeth, can be replaced throughout life. They inject venom with a quick strike, then retreat, following their prey until it dies. Sea-snakes have the fastest-acting and most lethal venoms as their fish prey can be lost unless it is ingested almost instantly.  

Viper venom, including that of Brazilian pit viper (Bothrops jararaca), rapidly lowers the blood pressure of their mammalian prey, so it faints and is easily swallowed. In an early example of what is now called biomimetics, analysis of the composition of this venom in the 1950s identified peptides that specifically inhibit angiotensin-converting enzymes (ACE) which led to the production of the first synthetic ACE inhibitors, now widely used to treat high blood pressure and related conditions in people and in elderly cats and dogs.  

All spiders (and most of other arachnids including scorpions) are predators, primarily on insects and other arthropods, though this exceptionally large tarantula occasionally catches small birds in its web. Spiders kill their prey by injecting venom that paralyses the nervous system from their paired chelicerae, but since its chemistry is adapted to kill arthropods, most spider venoms are harmless to people. Scorpions also prey mostly on other arthropods but some of the larger ones also kill small mammals and reptiles, hence their venom is toxic to humans.  

Most spiders ensnare prey with webs that consist of sticky proteins similar to silk that are secreted in large quantities from glands at the rear of the abdomen as the animal walks, forming patterns that differ between groups. Vibration receptors in the joints of their legs detect the disturbance when prey fly or walk into the web, then they run out and paralyse it, before secreting digestive enzymes into its body, the sucking up the liquified contents. Spiders ‘recycle’ damaged webs by eating them, but cobwebs remain after their creators have died. Jumping spiders do not make webs but see prey with their numerous eyes, then pounce on it. 

Octopus and squid are marine predators that catch crabs, other crustaceans, worms, small fish and sometimes each other. They grab their prey with the eight extensible/retractable arms and eat it with the stout beak. The most familiar, including this specimen, live in shallow coastal seas but cephalopods, especially squid, are most abundant and diverse in the deep ocean. Their large eyes are remarkably similar in structure to those of vertebrates. 

Many gastropod molluscs, such as this large helmet shell, are also predators, killing prey in warm shallow and around coral reefs by a variety of means, including injecting toxins. 

Most starfish (Echinodermata, Asteroidea) are predators such as this purple sea star from the Pacific; they wrap their arms around shelled molluscs, crustaceans, corals and other marine invertebrates, prise them open push the stomach containing digestive enzymes into the gap. 

In most fish and anuran amphibians (frogs etc.), the eggs are fertilized externally, often following complex courtship behaviour that synchronizes the release of gametes. Chondrichthyes (sharks, skates and rays), a few groups of bony Osteichthyes (and the earliest jawed fish, placoderms that were abundant in lakes 365 Mya) and all reptiles, birds and mammals have intromittent organs for internal fertilization, often followed by viviparity and/or parental feeding (see Glass Boxes B4 and C4). For efficient insemination, conspecific adults must identify, locate and court their mates and, when necessary, expel rivals. This Shelf shows a few of the anatomical structures involved. 

In mammals, the testes form inside the abdomen, but soon after birth they descend into the paired external scrotum which remains cool enough for efficient sperm production. This example is from an adult male springbok, note the fine, short hair on thin, flexible skin.  

The baculum, or os penis, differs from other long bones in lacking jointed ends and are often variable in shape with kinks and hooks. Those of the smallest species have a groove that contains the urethra, ensuring smooth passage of sperm even if the penis is bent or twisted. The bone is present in many, but not all, carnivores, pinnipeds (that of walruses is up to 0.75m long), rodents, lagomorphs, eulipotyphlans, chiropterans and most primates (see Glass Box A-D2 & D3), though it is very small in gorillas and chimpanzees and absent from humans. All perissodactyls, artiodactyls, cetaceans, elephants (see Glass Box A-C3, C2) also lack bacula.  

In this growth series from polar bears, the largest baculum is from the bear featured in Glass Box A2 who weighed over 400 kg, the brown bear was about the same, and all the other polar bears were at least 200 kg. The foxes weighed about 8 kg, the mature adult badger, coati and macaque monkey were 10-13 kg and the mink about 2 kg, so it's clear which species have the largest bacula in proportion to body mass. The conclusions from academic studies are that seasonal breeders, species with harems or multiple partners, and those that copulate for longest have proportionately large bacula, while its absence correlates with monogamy; but exactly when and why the bone disappeared from the ancestors of Homo sapiens remain under discussion. 

Secondary sex differences develop at or shortly before sexual maturity. Adult males of most cervids grow antlers (see Glass Box B3 and the mounted deer head) but those of primitive families, such as musk deer and water deer, grow curved tusks with sharp tips, formed from protruding upper canine teeth. In the skull of this juvenile Chinese water deer, the canines are just erupting, not yet externally visible. Smaller mammals, especially fossorial and nocturnal groups, rely more on pheromones and sound to demonstrate sexual status than on differences in appearance.  

In monkeys, apes (and to a less extent, humans) canine teeth are also sexually dimorphic and with the brow ridges over the eyes contribute to consistent sex differences in adult faces, as exemplified by these pig-tailed macaque monkeys, male Rt, and female Lt. In many higher primates, the texture and colour of the hair, and in mandrill baboons the colours of the facial and rump skin, enhance the sex differences in skeletal structure, as do beards and other sex and age differences in body hair of humans. A pad of fibrous adipose tissue under the scalp of senior male ‘silverback’ gorillas enlarges the top of the head, but the most extensive and visible sex differences in distribution of adipose tissue are found in humans between puberty and old age. 

Adult chelonians are sexually dimorphic for a different reason, how to fit together when copulating. As seen in these congeneric red- and yellow-footed Brazilian tortoises (which were together for more than 30 y and produced most of the eggs displayed in Glass Boxes A1, A4 and D4), mature females (left) grow bigger, have short tails, flat plastrons (base of shell) and carapaces (upper shell) shaped to hold as many eggs as possible, but the breeding males (centre Rt.), which are usually smaller, have longer, more muscular tails, a dipped plastron and often a clear waist to the carapace. Males introduce themselves by ‘bumping’ the female, and use the same tactic to expel rivals, behaviour that in a few species, such as this adult male desert gopher tortoise (far Rt.), is enhanced by deployment of the spur projecting from the front of the plastron to flip an opponent onto his back. 

Plumage, song and behaviour (dance, posture etc.) are the main agents of sexual dimorphism in birds. Adult males are the most colourful and flamboyant, at least during the breeding season, and usually slightly larger, though in larger species of owls, hawks, eagles and falcons, the females are significantly bigger than their mates.

The skins and skeletons of wild animals often show recent and healed injuries, congenital deformities or disease, although most museums conceal such imperfections in specimens on display.  

The clavicle (wishbone) of this black swan has a healed break that has formed a lump that has made the two halves asymmetrical; compare it with the homologous bones of the mute swan and the African grey parrot in Glass Box C4. The flight muscles attached to the clavicle probably re-organised themselves to at least partially compensate for the deformity.  

These abnormalities of the spine were found in skeletons of old male badgers. The sacrum (Lt) has an imperfectly healed breakage, possibly caused by a vehicle hitting the pelvis broadside on, badly displacing the left sacroiliac joint. The two lumbar vertebrae (Rt) are fused together by bone overgrowth, due to degenerative disease and/or injury. Compare these deformed badger bones with their homologues in the lion spine in Glass Box B4: normal lumbar vertebrae articulate freely, the holes containing nerves and blood vessels are unobstructed and the sacroiliac joints are symmetrical. These badgers apparently survived major injury and disease, though probably moved slowly and with a limp, for several months, perhaps years, until collected following fatal road accidents. 

This red-eared slider turtle is the same species as the one in Glass Box D1. From an early age, it was kept as a pet in Derbyshire and fed on fish caught from lakes and rivers of the Peak District. It grew very slowly and over several years became inert and anorexic until it died. Its shell, particularly the plastron, is severely deformed, possibly due to prolonged deficiency of iodine in its diet. This mineral, normally absorbed from food and water, is essential to the synthesis of thyroid hormones that control general metabolism and juvenile growth, especially of the brain and skeleton. Iodine deficiency during early human development produces cretinism, characterized by stunted growth, mental retardation, lethargy and other deformities and malfunctions.  

The bedrock under Derbyshire is hard limestone that precipitates the iodine ions in soil and natural springs & lakes into insoluble iodates, thus impairing the accessibility of the mineral to the ecosystems that they support. Cretinism and the related disorder goiter were common in the area until the first half of C19th when railways brought iodine-rich seafood inland. These diseases are now rare in the developed world because cooking salt is supplemented with small quantities of sodium iodide. But such precautions would not have benefited animals living on iodine-depleted food and water, so this turtle may have developed a similar syndrome. Organisms only prosper in habitats that provide all their nutritional requirements (see Glass Introduction to Herbivory). 

Teeth do not heal as efficiently as bones, so dental breakages and abscesses are long-lasting and may lead to starvation as in the donkey, shown in Glass Box A3, and the deer in Glass Box B3. This female timber wolf was about 8 y old, the canine teeth in both her lower jaws are worn blunt (compare them with the young male in Glass Box B2). The two holes in both jaws just behind the canine teeth contained the mandibular nerves that supplied the jawbone, lower lips and associated muscles. The right jaw (front) has several additional holes with abnormal bone around them and the largest molar tooth is loose and has moved upwards. These features, not seen in the left jaw, are all evidence for chronic bacterial infection in the jawbone that probably began in the tooth socket and would have led to prolonged pain and the tooth falling out, impairing the bite. Among social mammals like badgers and wolves, sick or injured group members may benefit from food acquired by others, thus extending their lives for longer, as happens among humans. 

Similar processes may have been more advanced in this elderly mouflon which has missing molar teeth and bone in both upper and lower right jaws, probably caused by abscesses developing under molar teeth that eroded the surrounding bone, producing large holes that must have weakened both jaws. The whole skull is very light, as is that of the donkey in Glass Box A3, from depletion of proteins for energy generation. 

Similar dental abscesses also occur in other mammals including people. The major changes in diet that followed agriculture and domestication of livestock (see Glass Box C1) may have increased their frequency; tooth wear and infections are observed in many Ancient Egyptian mummies and similar burials. Until the mid C20th, tooth extraction was the only means of relieving the pain, preferably before the infection had spread into the bone. 

In general, invertebrates heal and regenerate tissues more effectively than vertebrates. The shell of this giant African land snail shows many layers of reformation after wear or damage, so it appears thick and irregular compared to those in Glass Box D1.  

Reindeer are specialist arctic deer that during warmer periods of the Pleistocene Ice Age had circum-polar distribution. Mainland reindeer (called caribou in N. America) form large herds that migrate long distances, spending the summer grazing on tundra, where the fawns are born, and winters in more sheltered forested areas that provide reindeer moss and other lichens. Reindeer hooves are broader and softer, more like paws, than the hooves of other cervids, thus better suited to moving on snow and ice.  Adults of both sexes grow antlers, though those of males become much larger (see back of Box A1); males shed their antlers after the autumn mating season but females retain theirs until the spring, perhaps as a means of competing for scarce food.  

Many isolated populations (recognized mainly by sub-fossils showing different body sizes and antler shapes) formed on islands, valleys etc, then disappeared as the climate warmed or cooled, causing often abrupt changes in food supply and predator access. One such subspecies, Svalbard reindeer, have lived on the mountainous, treeless Svalbard archipelago (77-80 oN) without the wolves and lynx that prey on mainland reindeer, since the Barents Sea (between it and N Norway) thawed at the end of the last glaciation about 12 Kya. The reindeer and arctic fox (see Glass Box B2) are the only indigenous mammals on Svalbard (other species were introduced by humans during C20th).  

The subspecies has evolved to be non-migratory, herds are replaced with small groups that are unafraid of strangers, and all fawns are born in the same week in early June, taking advantage of new vegetation growth during the brief summer. Compared with mainland reindeer, they are small, slow moving, with greatly reduced antlers, shorter ears & tail, thick hair, very efficient digestion, eyes in which the cornea and lens transmit UV light reflected from snow, and the tapetum, the reflective layer behind the retina, changes from summer gold to winter blue, thus maximizing the capacity to find food. The small, in-bred populations have a high incidence of minor skeletal abnormalities such as vestigial antlers and dental anomalies. The Svalbard reindeer skull on the left had grown two antlers (now sawn off), while that on the right has one small, simple antler, but the other has failed to grow, leaving a small bony cone. The last molar in the left jaw of the centre skull is rotated. 

The reindeer eat as much as they can find during the brief summer, depositing storage fats in their white adipose tissue which can reach more than 25% of the total body mass (compared to 2-8% in most mammals). When winter returns in late August, they dig through the snow to reach the dead vegetation underneath. After this resource is exhausted or becomes utilise their stored fat while waiting for the snow to melt in late May. These ways of surviving long winters are only possible in the absence of predators. 

The outer guard hairs are stiff enough to disrupt airflow, thus reducing heat loss during strong wind, shed snow & rainwater and provide mechanical protection. Those of arctic, high-altitude and aquatic species such as polar bears and small seals (see Glass Box C3), often thick walls around spongy, air-filled cores, making them stiff and strong but light, and conferring additional buoyancy. In winter, reindeer pelts consist of very long, quite stiff guard hairs that are dense enough to form a stout but flexible waterproof covering over the thick underfur. Compare the sample of Svalbard reindeer hair with that of the domesticated reindeer and roe deer (see also Glass B4): both have thinner, and in the roe deer, shorter, guard hairs because they live in more temperate climates.  

NB This Collection does not hold the reindeer lower jaws because soon after collection, they were labelled and deposited with the Wildlife Conservation Authorities on Svalbard; the lower jaw of polar bear in Glass Box A2 is still in Nunavut, Canada for similar reasons.

The Glass Cabinets emphasize teeth and jaws for food acquisition and nutrition, but skins also play a part and mammalian fur has other essential roles in ecosystems.  

Pollen, seeds and other plant material stick to mammalian fur (see also Glass Box D4). Flowers attract mammalian pollinators to sweet nectar primarily with scent; flowers pollinated by bats (see Glass Box D2) are usually white and open at night with nectaries accessed by climbing inside, so their furry bodies are coated with pollen. Rainforest monkeys and, on Madagascar, lemurs climb between tall trees, collecting nectar and pollen, some of which sticks to their fury faces and paws, thus pollinating the flowers over long distances. Small primates such as lorises and galagos (= bushbabies), some murid rodents and, in Australasia, possums transmit pollen between understory trees. As well as nectar, most such mammals eat some of the pollen, which is rich in proteins and fats. 

Mammals disperse seeds in many ways, via the gut, unclaimed storage middens and stuck to fur with hooked burrs, where they can reduce running speed and compromise camouflage by rubbing against other plants.  

Almost all terrestrial mammals harbour fleas, lice and mites and ticks, all of which can irritate the skin and/or transmit pathogens. Flea larvae feed on skin debris under mammalian fur (or in skinfolds and ears of hairless mammals such as elephants and spiny ones like hedgehogs) but the adults, which pierce the skin to suck blood, can jump from host to host and onto other species: cat fleas often bite humans but cannot complete their lifecycle except on a cat. Lice, which are also insects, spend their whole life on mammalian skin which they pierce to suck blood, resisting expulsion with sticky eggs (‘nits’) and hooked legs that closely fit the thickness of their hosts’ hair. Ticks, which are arachnids not insects, suck blood from several hosts in succession, sometimes including reptiles and amphibians, so are ideally placed for transmitting pathogens between major groups. Their smaller relatives, mites, mostly breed on debris, unwashed clothing or furnishings. Such ‘resident’ parasites and flying insects, including mosquitoes, tsetse flies and botflies (which lay eggs in mammalian skin), cause intense irritation and hair shedding, thus impairing well-being, body insulation and appearance.  

Equids and bovids (including domestic horses and cattle swish long hairy tails and twitch the dermal muscles in the skin thus transiently deterring such flying insects before they attack but cannot eliminate them. The only dense hair on adults of most rhinoceros species is this little tail fan, plus eyelashes and clumps in the ears; they protect exposed but ungroomable vital tissues from insect attack. 

Grooming removes loose hair, plant seeds & debris, ectoparasites and their eggs, cleans off the scent of blood and other prey remains and keeps the hair smooth for silent, efficient movement. Many mammals roll on rough ground or rub themselves against trees and scratch their skin with their hooves or clawed paws (as dogs do), reserving licking for wounds and sores. But for felids, keeping claws sharp is very important, so they mainly groom with the tongue. The numerous little hooks on the tongue of this young tiger match the thickness of its guard hairs, thus licking cleans and straightens the coat like a comb. Other species have hooks on their tongues that match the dimensions of their hair. Cats and dogs selectively bred for long hair (see Glass Box C1) need frequent combing as their natural grooming ‘tools’ may be inadequate. 

Thermal insulation when sleeping in cold weather is balanced against dissipation of excess heat while chasing, or being chased, in the heat of the day. Erecting or flattening the guard hairs and adjustments to blood perfusion of the skin and extremities (see Glass Box C2) help to retain or lose heat, as does evaporative cooling by panting, spreading saliva over the coat and sweating. These fragments of skin and hair from brown and polar bears and a lion and a cheetah illustrate some adaptations of hair to climate, habitat and habits. The bears have thick coarse coats suitable for sleeping outside in the cold, but they do not pursue prey over long distances in warm weather; they can die from overheating if chased by predators or people. Lions’ thick skin is protective and the stiff but sparse hair collects less debris as they stalk prey through dense undergrowth and long grass, and can dissipate excess heat during daytime hunts. Cheetahs have short, easily erected guard hair and long thinly-haired limbs; they can chase prey until it falters from exhaustion and overheating, without doing so themselves.  

Small mammals, especially arctic and semi-aquatic species with long narrow bodies have the warmest, silkiest fur; for example, squirrel and rabbit pelts have fine, soft guard hairs over dense underfur, as do arctic fox, mink and ermine (= stoat). Wolverines are mustelids resembling badgers but larger, fiercer and solitary. They hunt and scavenge year round in northern Canada, Scandinavia and Russia. For reasons that are still not completely understood, frost can be very easily shaken off their thick long fur. These species and coypus, sea otters, foxes, especially arctic foxes (see Glass Boxes A2, B2 & D3), have long been hunted, some later captive bred, to produce pelts for human use (see Glass Box D1). About 50 mink are needed for a full-length coat, hundreds of ermine form a cape.  

Camel hair feels soft and is dense, light and springy, holding many tiny pockets of air that hold body heat against the cold, while allowing its dissipation in hot weather. Domestication of camels and reindeer has not progressed to selection for producing a fleece, so like the wild mammals, they moult naturally in spring and are not shorn. The hair is then collected to make high-value human clothing. 

The American species of beaver (see Glass Box D3) ranges over Canada and much of USA including Alaska, and the European species is found in Scandinavia, northeast Europe and much of western Russia. They can grow to 30 kg body mass and swim by up and down movements of the hind limbs and the large flat scaly tail, which is also ‘slapped’ on water to warn others of danger. The hairless tail is kept from freezing by parallel blood vessels acting as heat exchangers a mechanism similar to that of birds’ unfeathered legs (see Glass Box C4). The head, limbs and body have hair similar to that of reindeer; an outer layer of long straight guard hairs, overlying exceptionally dense underfur, consisting of fine strands interlocked with tiny hooks, together forming a tough, warm, waterproof coat for life in sub-arctic streams, forests and mountains.  

The guard hairs can be plucked or rubbed off to produce pelts with soft warm fur, or the underfur sheared off, heated and compacted to produce felt, a firm, durable, waterproof material, ideal for making tall gentlemen’s hats. From the C16th-C19th native people in North America, Scandinavia and Russia hunted and trapped beaver for their meat, incisor teeth and skins. Many pelts were used locally but when felt hats became fashionable, huge numbers were sold to traders and exported throughout urban Europe and America. The indigenous Eurasian species, Castor fiber soon disappeared from Europe and much of Russia, but has recently been re-introduced into its former range, including parts of UK and has increased since hunting stopped.  

Other skins were valued more for their glamorous appearance than insulation properties. Spots and stripes camouflage the predator from the prey, especially in trees or dense undergrowth and under dim or variable light. Jaguars, about the same body mass as humans, hunt mainly at night in various habitats of lowland South and Central America, especially near and in swamps and rivers. Their short hair absorbs little water or debris and varies in colour, with a few being nearly black. 

Tigers are twice the size of the New World felids and until recently inhabited a much wider range, from tropical India and Southeast Asia to Caucasus, China and southern Siberia, from lowland forests and swamps to high mountains. They often hunt at night, using excellent hearing and olfaction and several groups of sensitive whiskers.  Bilateral symmetry of the stripes on the body and face arises because the melanocytes that produce the black pigment in the skin form early in embryonic development, moving out from the midline.  

In this tiger face and that of the brown bear, hair covering the nose and lips is shorter, thinner and stiffer compared to the thick insulating fur over the cranium. Mammalian noses remain cool to reduce water loss from the lungs during respiration; noses and ears also dissipate excess heat efficiently, helping to protect the brain and eyes, which can be severely damaged by high temperature. Olfaction is so important that even the large nose of this brown bear is hairless, as are those of polar bears, wolverines and mink; rich blood perfusion prevents exposed noses from freezing, though these hardy arctic mammals save energy by tucking their snouts into their fur while sleeping. 

Tiger, bear and wolverine pelts are very hard wearing but the thick skin and long coarse guard hairs make them stiff and heavy, limiting their use to hats, trimmings and furnishings, but many types of synthetic clothing, including coats, imitate the appearance. Skins and hair from large mammals, bison, bears, wolves etc. are warm and strong; they have been used as bedding for tens of thousands of years, but they are rough and heavy. The tall bearskin hats of the ceremonial uniforms of certain UK army regiments are mostly made from pelts of black bears (see Glass Box A2), which are still widespread, and in places abundant across USA and Canada. 

In all terrestrial mammals, hair and skin parasites pass between conspecifics at copulation, from mother to offspring and between mates. But cohabiting of social species such as badgers creates more opportunities for parasites. Their thick, tough skin and sparse, bristly hair harbour ticks, lice and specialised fleas that are found on no other species. Badgers move from one sleeping site to another within their extensive sett, and avoid sleeping in each other’s ‘bed’. From time to time, the colony brings their ‘bedding’ of moss, grass and twigs to the surface to ‘air’ or replace it entirely. These habits probably reduce, but cannot eliminate, parasite infestation.  

Guard hairs have evolved into protection from predators: those of African porcupines form sharp stout spines (the longest of this bunch is 0.35 m), incorporating bands of melanocytes to form stripes. The roots are relatively weak, so after the tips penetrate an attacker’s skin, the bases break easily, leaving the spines embedded. Wild boar skin is thick and its guard hairs have become stiff bristles, almost impenetrable by predators’ canine teeth or sharp claws. People have long used the bristles from both wild boar and badgers for making brushes to groom themselves. 

At least part of the skin of almost all reptiles, birds and a few mammals forms scales. The lower legs and feet of armadillos are covered with reptile-like scales, affording stout, flexible protection against stinging insects enraged by intrusion into their nest (see Glass Box D2). Scales on bird legs are described in Glass Box C4. 

The keratinous scales on the flipper skin of this marine green turtle differ in size and shape, allowing the underlying structures to move freely while maintaining protection; note also the sharp claws at the tip of each digit (see also Glass Box D2).  

The larger skin is from the python shown in Glass Box D2. The other is probably a rat snake, long, agile, non-venomous colubrids of variable colour and pattern that are widespread in USA east of the Rocky Mountains. They also kill their prey, mostly rodents (see Glass Box D3), lizards and nestling birds, by constriction but by repeated squeezing that impedes blood circulation rather than crushing the thorax as pythons and other boids do. 

Both these skins show the smooth patterned back and rows of wide ventral scales (see also Glass Box D4), characteristic of the suborder Serpentes, that are essential to all their various forms of locomotion. Large snakes can enter narrow holes and glide through dense undergrowth in an almost straight line: concertina-like waves of muscle contraction pull forward groups of ribs plus the overlying skin, and the smaller dermal muscles adjust the scales so they grip the substrate as required. These structures are also used for faster movement by lateral undulation, and enable snakes to climb by coiling part of the body around branches.  

Snakes shed the outer keratinous layer of skin several times a year, often loosening it by rubbing against rough surfaces, then moving forward leaving the old skin inside out. In the shed skin of this garter snake (also a colubrid), the wide ventral scales are clearly visible; their keratinous layers are thicker than those of the smaller scales on the back so have not disintegrated as much. Shedding replaces wear and damage, disposes of external parasites and accommodates growth, so most juveniles shed more frequently. 

Lizard scales are usually smaller and the skin thicker than those of snakes. The outer layer is shed in small patches, rather than as a single sleeve as in snakes. Monitor lizards are a genus of semi-aquatic, fast-running lizards, found in most of Africa, Australia and southern Asia, where they eat a wide range of prey and carrion. Many of the 80 species are large, the Komodo dragon grows up to 3 m long, so they make spectacular pets, which is believed to be the source of several species becoming destructive invaders in Florida, and parts of southeast Asia. Indigenous people have long harvested monitors for their meat and thick, durable skins. This ‘lizard skin’ wallet, which is probably a by-product of efforts to exterminate invasive monitors, shows the small scales arranged in rows from the midline over the spine. 

Reptile scales almost always contain pigments and/or in certain snakes, crystalline materials that are iridescent, making the skin shimmer. Some have bright colours that form elaborate patterns, e.g. the rattlesnake in Glass Box D2 and here, tortoises in Glass Box D3 and above, and the lizard in Glass Box D4. Tests show that lizards, tortoises and many snakes have good colour vision, better than that of most mammals. These observations have prompted the suggestion that dinosaurs and other Mesozoic reptiles were also brightly coloured.  

Most leather is prepared from skins of large domesticated bovids, cattle, buffalo, sheep and goats, but for certain purposes, skin from pigs, deer and horses is also used. The skin of juvenile mammals is thinner with less dense collagen fibres, so is softer and more supple than that of adults, hence ‘kid gloves’ made from young goats, but it is also less tough and hard-wearing. Parchment, and the smoother, whiter grade vellum, was made from the skins of sheep, goats and calves. It served as the main writing material for millennia and is still used for certain documents. 

At the other end of the scale, leather made from camel hide is among the most expensive, being strong, waterproof and hard-wearing but also flexible and easily polished to a high shine. One of the consequences of selecting domestic livestock for fast growth and hence early maturation is that their skins are thinner and thus make weaker leather. This old key fob is strong leather, thick enough to be embossed, so probably made from the hide of a large adult bull.  

Relative to body mass, human skin, especially that of women and children, is very thin and weak; as in other mammals, the colour, thickness, density and distribution of body hair change with age and may differ with ancestry.  

NB Except where otherwise stated, the skins shown on the lower shelves were dried in air or using table salt and treated with domestic moth proofers, so the pelts are stiff but retain their natural colours. Professional leather tanners and furriers use a wide range of preparation methods and chemicals.